With the rapid development of Ethernet technique, Ethernet communication is widely used in more and more communication systems. Ethernet has the advantages of popular usage, mature technology and low cost, and the communication speed of Ethernet communication is obviously superior to that of other conventional serial communications.
Presently, the Ethernet communication is used in some control systems, such as some numerical control systems. The control system includes at least one control device and at least one measuring and actuating equipment, with one control device controlling at least one measuring and actuating equipment.
In practical applications, Ethernet generally sends data by using Carrier Sense Multiple Access (CSMA)/Collision Detection (CD) mechanism. Specifically, each node (including the control device and the measuring and actuating equipment) inside the control system listens to the channel, and the node desired for data transmission can only send data when the channel is free.
However, if multiple nodes send data at the same time, then there may be transmission collision, so that some nodes or all the nodes desired for data transmission fail to send data.
One existing method for solving the above problem caused by collision is that, once a transmission collision is detected, the node desired for data transmission will back-off, that is to say, retrying the transmission after a period of time.
However, it is discovered by the inventors upon studying the above solution that, when the node desired for data transmission retries the transmission after a period of time, there is still possibility for transmission collision, and thus the node desired for data transmission can only wait for another period of time to retry the transmission. If this phenomenon continues, the node desired for data transmission is prevented from data transmission for quite a long time; it is even not sure when the transmission can take place. Therefore, the problem of transmission collision can not be radically solved by the existing back-off mechanism.